This invention relates to a fixing apparatus which has a heating roller having a heating means inside and a pressing roller being in pressure contact with said heating roller, and makes a transfer material having a toner image transferred on it pass between the above-described heating roller and pressing roller to thermally fix said toner image to said transfer material.
In conventional fixing apparatus, when the driving operation for the heating roller is stopped at the time of completion of the fixing operation, occurrence of jams, etc., the heating operation for the heating means equipped on the heating roller is also stopped at the same time.
In the abovementioned fixing apparatus, however, a quantity of heat being necessary during driving the heating roller is greater than a quantity of heat being necessary during stopping the heating roller, due to influence of loses of heat dispersing to the pressing roller and into the ambient atmosphere.
Accordingly, in case that the hating means is still driven just before the heating roller is stopped, the heating roller stores an excessive quantity of heat in it after it stops.
There has been a problem that, as shown in FIG. 27, when the heating roller stops in the abovementioned situation, a transient overshoot (to exceed a predetermined temperature) is generated in the temperature characteristic on the surface of the heating roller due to the excessive quantity of heat, resulting in deterioration of the surface layer durability of the heating roller and activation of an extraordinary high-temperature alarm of the fixing apparatus.
In addition, recently, the thickness of the heating roller base body has been made as thinner as possible to reduce its heat capacity in the saving energy point of view.
In this case, as shown in FIG. 28, the thinner the thickness of the heating roller base body, the larger the amount of the overshoot.
To overcome the abovementioned drawbacks in conventional fixing apparatus, it is an object of the present invention to provide a fixing apparatus, which makes it possible to suppress a temperature overshoot of the heating roller when the heating roller is stopped.
Accordingly, to overcome the cited shortcomings, the abovementioned object of the present invention can be attained by fixing apparatus and image-forming apparatus described as follow.
(1) A fixing apparatus, comprising: a heating roller; a heating element disposed in the heating roller; a pressing roller pressure-contacting the heating roller to fix an image onto a transfer sheet passing through a pressure-contacting section between the heating roller and the pressing roller; and a cooling device to cool the heating roller; wherein the cooling device is activated during a predetermined time period after consecutive fixing operations are completed.
(2) The fixing apparatus of item 1, wherein the consecutive fixing operations correspond to a number of prints included in a JOB designated in advance.
(3) The fixing apparatus of item 1, wherein a cooling region cooled by the cooling device is variable in a longitudinal direction of the heating roller.
(4) A fixing apparatus, comprising: a heating roller; a heating element disposed in the heating roller; a pressing roller pressure-contacting the heating roller to fix an image onto a transfer sheet passing through a pressure-contacting section between the heating roller and the pressing roller; a temperature detecting device to detect a temperature of the heating roller; and a cooling device to cool the heating roller; wherein the cooling device is activated after consecutive fixing operations are completed, so as to lower the temperature of the heating roller to a predetermined temperature based on a result detected by the temperature detecting device.
(5) The fixing apparatus of item 4, wherein the consecutive fixing operations correspond to a number of prints included in a JOB designated in advance.
(6) A fixing apparatus, comprising: a heating roller; a heating element disposed in the heating roller; a pressing roller pressure-contacting the heating roller to fix an image onto a transfer sheet passing through a pressure-contacting section between the heating roller and the pressing roller; and a cooling device to cool the heating roller; wherein, in case of a jam occurrence, the heating element is deactivated and the cooling device is activated until a jam-processing is completed.
(7) The fixing apparatus of item 6, further comprising: a temperature detecting device to detect a temperature of the heating roller; wherein the cooling device is deactivated either when the jam processing is completed or when the temperature of the heating roller is lowered to a predetermined temperature based on a result detected by the temperature detecting device.
(8) The fixing apparatus of item 6, wherein the cooling device is deactivated either when the jam processing is completed or when a predetermined time period has elapsed.
(9) The fixing apparatus of item 6, wherein a cooling region cooled by the cooling device is variable in a longitudinal direction of the heating roller.
(10) An image-forming apparatus, comprising: a heating roller; a heating element disposed in the heating roller; a pressing roller pressure-contacting the heating roller to fix an image onto a transfer sheet passing through a pressure-contacting section between the heating roller and the pressing roller; and a cooling device to cool the heating roller; and a control section to activate the cooling device during a predetermined time period after consecutive fixing operations are completed.
(11) The image-forming apparatus of item 10, wherein a cooling region cooled by the cooling device is variable.
(12) The image-forming apparatus of item 11, wherein the cooling device comprises a plurality of fans arrayed in a longitudinal direction of the heating roller, and the image-forming apparatus further comprising: a cooling region varying device to shade the heating roller from wind blown by several fans included in a plurality of the fans, in order to vary a cooling region cooled by the cooling device.
(13) An image-forming apparatus, comprising: a heating roller; a heating element disposed in the heating roller, a pressing roller pressure-contacting the heating roller to fix an image onto a transfer sheet passing through a pressure-contacting section between the heating roller and the pressing roller; a temperature detecting device to detect a temperature of the heating roller; a cooling device to cool the heating roller; and a control section to activate the cooling device after consecutive fixing operations are completed, so as to lower the temperature of the heating roller to a predetermined temperature based on a result detected by the temperature detecting device.
(14) An image-forming apparatus, comprising: a heating roller; a heating element disposed in the heating roller; a pressing roller pressure-contacting the heating roller to fix an image onto a transfer sheet passing through a pressure-contacting section between the heating roller and the pressing roller; a cooling device to cool the heating roller; a jam-detecting device to detect a jam occurrence; and a control section to deactivate the heating element and to activate the cooling device when the jam-detecting device detects the jam occurrence, until a jam-processing is completed.
(15) The image-forming apparatus of item 14, further comprising: a door member to be opened and closed when the jam-processing is performed; and a door status detecting device to detect an opened or closed status of the door member; wherein the control section deactivates the cooling device and activates again the heating element when the jam-detecting device detects a completion of the jam-processing and the door status detecting device detects the closed status of the door member.
(16) The image-forming apparatus of item 14, further comprising: a temperature detecting device to detect a temperature of the heating roller; wherein the control section deactivates the cooling device either when the jam-processing is completed or when the temperature of the heating roller is lowered to a predetermined temperature based on a result detected by the temperature detecting device.
(17) The image-forming apparatus of item 14, wherein the control section deactivates the cooling device either when the jam-processing is completed or when a predetermined time period has elapsed.
(18) The image-forming apparatus of item 14, wherein a cooling region cooled by the cooling device is variable.
(19) The image-forming apparatus of item 18, wherein the cooling device comprises a plurality of fans arrayed in a longitudinal direction of the heating roller, and the image-forming apparatus further comprising: a cooling region varying device to shade the heating roller from wind blown by several fans included in a plurality of the fans, in order to vary a cooling region cooled by the cooling device.
(20) An image-forming apparatus, comprising: a heating roller; a heating element disposed in the heating roller; a pressing roller pressure-contacting the heating roller to fix an image onto a transfer sheet passing through a pressure-contacting section between the heating roller and the pressing roller; a fixing output detecting device, disposed at a downstream side with respect to the pressure-contacting section in a conveyance direction of the transfer sheet, to detect a passage of the transfer sheet; and a control section to control the heating element; wherein, when the fixing output detecting device detects a passage of a final transfer sheet included in a prescribed job, the control section switches a threshold value for controlling a fixing temperature to a lower value than that during a fixing operation, before deactivating a rotation of the heating roller.
(21) An image-forming apparatus, comprising: a heating roller; a heating element disposed in the heating roller; a pressing roller pressure-contacting the heating roller to fix an image onto a transfer sheet passing through a pressure-contacting section between the heating roller and the pressing roller; a temperature detecting device to detect a temperature of the heating roller; a fixing output detecting device, disposed at a downstream side with respect to the pressure-contacting section in a conveyance direction of the transfer sheet, to detect a passage of the transfer sheet; and a control section to control the heating element; wherein, when the fixing output detecting device detects a passage of a final transfer sheet included in a prescribed job, the control section deactivates the heating element before deactivating a rotation of the heating roller and continues deactivating the heating element until the rotation of the heating roller is deactivated.
Further, to overcome the abovementioned problems, other fixing apparatus, embodied in the present invention, will be described as follow:
(22) A fixing apparatus, characterized in that, in the fixing apparatus, which comprises a heating roller having a heating means, serving as a heating element, in it and a pressing roller pressure-contacting the heating roller to fix a toner image, transferred on a transfer sheet, with heat onto the transfer sheet by passing the transfer sheet between the heating roller and the pressing roller, a cooling means, serving as a cooling device, for cooling the heating roller and a control section for activating the cooling means during a predetermined time period after the fixing operation is completed are provided.
Since the control section continues to activate the cooling means during a predetermined time period after the fixing operation is completed, the temperature overshoot of the heating roller can be suppressed when the heating roller stops.
Incidentally, the abovementioned passage of xe2x80x9cafter the fixing operation is completedxe2x80x9d is equivalent to a passage of xe2x80x9cafter consecutive fixing operations are completedxe2x80x9d, or equivalent to a passage of xe2x80x9cafter fixing operations necessary for a designated job are completedxe2x80x9d. Further, although the control section can determine the completion of the fixing operation, for instance, based on a result, detected by a sensor equipped in the fixing apparatus, that all transfer sheets required for one designated job has passed, it is also possible to determine the completion of the fixing operation based on a result that a motor for driving the rotation of rollers of the fixing apparatus stops.
(23) A fixing apparatus, characterized in that, in the fixing apparatus, which comprises a heating roller having a heating means in it and a pressing roller pressure-contacting the heating roller to fix a toner image, transferred on a transfer sheet, with heat onto the transfer sheet by passing the transfer sheet between the heating roller and the pressing roller, a temperature detecting means, serving as a temperature detecting device, for detecting a temperature of the heating roller, a cooling means for cooling the heating roller, and a control section for activating the cooling means until the temperature of the heating roller reaches to a predetermined temperature after the fixing operation is completed by receiving temperature information from the temperature detecting means, are provided.
Since the control section continues to activate the cooling means until the temperature of the heating roller reaches to a predetermined temperature after the fixing operation is completed by receiving the temperature information from the temperature detecting means, the temperature overshoot of the heating roller can be suppressed when the heating roller stops.
(24) A fixing apparatus, characterized in that, in the fixing apparatus, which comprises a heating roller having a heating means in it and a pressing roller pressure-contacting the heating roller to fix a toner image, transferred on a transfer sheet, with heat onto the transfer sheet by passing the transfer sheet between the heating roller and the pressing roller, a cooling means for cooling the heating roller, and a control section for deactivating the heating means of the heating roller at the time of the jam-occurrence by receiving jam-information and continuing to activate the cooling means until the jam processing is completed, are provided.
Since the control section deactivates the heating means of the heating roller at the time of the jam-occurrence and continues to activate the cooling means until the jam processing is completed, the temperature overshoot of the heating roller can be suppressed when the heating roller stops.
Incidentally, the jam-processing is regarded as being completed when the jam-detecting device detects a completion of the jam-processing and the door status detecting device detects the closed status of the door member to be opened and closed when the jam-processing is performed.
(25) A fixing apparatus, characterized in that, in the fixing apparatus, which comprises a heating roller having a heating means in it and a pressing roller pressure-contacting the heating roller to fix a toner image, transferred on a transfer sheet, with heat onto the transfer sheet by passing the transfer sheet between the heating roller and the pressing roller, a temperature detecting means for detecting a temperature of the heating roller, a cooling means for cooling the heating roller, and a control section for deactivating the heating means of the heating roller at the time of the jam-occurrence by receiving the jam-information and continuing to activate the cooling means either until the temperature of the heating roller reaches to the predetermined temperature or until the jam processing is completed by receiving temperature-information from the temperature detecting means, are provided.
Since the control section deactivates the heating means of the heating roller at the time of the jam-occurrence and continues to activate the cooling means either until the temperature of the heating roller reaches to the predetermined temperature or until the jam processing is completed, the temperature overshoot of the heating roller can be suppressed when the heating roller stops.
Incidentally, it is possible to prevent the temperature of the heating roller from excessively decreasing lower than a necessary temperature level and to minimize the influence exerted to the fixing operations to be performed since then by deactivating the cooling means either when the temperature of the heating roller reaches to the predetermined temperature or when the jam-processing is completed after the jam occurrence. Further, it is also possible to obtain the same effect as that mentioned above by deactivating the cooling means either when a predetermined time period has elapsed or when the jam-processing is completed after the jam occurrence.
(26) A fixing apparatus, characterized in that, in the fixing apparatus, which comprises a heating roller having a heating means in it and a pressing roller pressure-contacting the heating roller to fix a toner image, transferred on a transfer sheet, with heat onto the transfer sheet by passing the transfer sheet between the heating roller and the pressing roller, a cooling means for cooling the heating roller, and a control section for deactivating the heating means of the heating roller at the time of the jam-occurrence by receiving the jam-information and continuing to activate the cooling means either during the predetermined time period or until the jam -processing is completed, are provided.
Since the control section deactivates the heating means of the heating roller at the time of the jam-occurrence and continues to activate the cooling means the temperature overshoot of the heating roller can be suppressed when the heating roller stops.
(27) The fixing apparatus cited in any one of items 22-26, characterized in that the cooling region of the cooling means is variable in the longitudinal direction of the heating roller.
Since the cooling region of the cooling means is variable in the longitudinal direction of the heating roller, it becomes possible to cool all over the heating roller to suppress its temperature overshoot when the heating roller stops.
Further, when the fixing operation repeatedly conducted for fixing a large number of transfer sheets having a narrow width, it is also possible to cool only the end portion of the heating roller to prevent the end portion of the heating roller from over heating.
(28) A fixing apparatus, characterized in that, in the fixing apparatus, which comprises a heating roller having a heating means in it and a pressing roller pressure-contacting the heating roller to fix a toner image, transferred on a transfer sheet, with heat onto the transfer sheet by passing the transfer sheet between the heating roller and the pressing roller, a temperature detecting means for detecting a temperature of the heating roller, a fixing-output detecting means, serving as a fixing-output detecting device, disposed at the outlet for detecting a passage of the transfer sheet, and a control section for deactivating the heating means of the heating roller when the final recording-paper has passed and setting the threshold value of the fixing control temperature at a value lower than the temperature during the fixing operation, are provided.
Since the control section receives the information from the fixing-output detecting means and deactivates the heating means of the heating roller when the final recording-paper has passed, namely, before outputting the instruction for stopping the heating roller, and sets the threshold value of the fixing control temperature at a value lower than the temperature during the fixing operation, the temperature overshoot of the heating roller can be suppressed when the heating roller stops.
In short, the action for driving the heating means is stopped by switching the threshold value of the fixing control temperature to a lower value.
(29) A fixing apparatus, characterized in that, in the fixing apparatus, which comprises a heating roller having a heating means in it and a pressing roller pressure-contacting the heating roller to fix a toner image, transferred on a transfer sheet, with heat onto the transfer sheet by passing the transfer sheet between the heating roller and the pressing roller, a temperature detecting means for detecting a temperature of the heating roller, a fixing-output detecting means disposed at the outlet for detecting a passage of the transfer sheet, and a control section for deactivating the heating means of the heating roller when the final recording-paper has passed by receiving information from the fixing-output detecting means, are provided.
Since the control section deactivates the heating means of the heating roller when the final recording-paper has passed by receiving information from the fixing-output detecting means, namely, during the period from the time before the heating roller stops to the time when the heating roller stops, the temperature overshoot of the heating roller can be suppressed when the heating roller stops.